FERTILIZING AND WATERING TREES 5 



In many areas it is not desirable, beneficial, or economical to 

 apply all three primary nutrients. Each of the three can be pur- 

 chased separately. 



The value of organic vs. inorganic fertilizer materials is 

 discussed fully in other publications (see selected references). 

 The organic sources contain a much lower percentage of nu- 

 trients, are slower to release nutrients, are more difficult to ob- 

 tain and apply, and are more expensive per pound of nutrient 

 received. Those organic fertilizer materials containing humus, 

 such as manure or composts, have some advantage in improving 

 soil aeration, structure, and water-holding capacity. When plant 

 nutrients are of primary interest, the economics of fertilizing 

 definitely favor inorganic fertilizers. 



SHOULD YOU FERTILIZE? 



A number of factors should be considered before fertilizing 

 trees. The general condition and color of the plants must be 

 noted. If trees have poor growth or pale green leaves, fertilizer 

 may make them grow faster and give them a darker green color. 

 If trees are attacked by canker-causing fungi or borers, fertilizer 

 will make them more vigorous and less subject to these troubles. 



Determine the rate of annual growth 



The amount of annual shoot growth of a tree can be easily 

 determined on tree species with terminal bud scale scars. Bud 

 scales enclose and protect buds on the ends of twigs during the 

 winter and leave scars that encircle the twig after the scales fall 

 in the spring. These scars remain evident for several years on 

 many tree species. 



From the tip of the branch to the ring of bud scale scars near- 

 est the tip is the current season's growth. The growth of previous 

 years can be determined by observing the distance from bud 

 scale scars to bud scale scars as they occur down the twig (Fig. 

 1). By observing the length of growth for the preceding 3 or 4 

 years on several twigs, it is possible to estimate whether the 

 growth rate is satisfactory or unsatisfactory, increasing or de- 

 creasing. 



The growth rate will vary with tree species, soil type, and 

 environmental conditions. As a general guide, terminal twig 

 growth on most trees should be 9-12 inches or more a year. Trees 

 approaching mature size may grow only 6-9 inches a year. 



